net:
* increase queue size to 1024 (more stable on Linux)
* use mac address from Nic session instead of random one
* handle data that is larger than rx descriptor correctly (copy less)
* clear descriptor header (12 bytes) on rx
generic:
* always use 'avail_idx' (tx and rx)
* added barriers when reading/writing queues (TMP)
Ref #3620
We do not use the VMM with several CPUs until now.
On the other hand there is a dead-lock due to the
generic timer calling the cpu handler function explicitly,
which already holds the lock. For the time-being remove the lock.
Ref #3620
